Phase 1 Exchange

The Phase 1 exchange is known as Main Mode. In the Phase 1 exchange, IKE uses public-key encryption methods to authenticate itself with peer IKE entities. The result is an ISAKMP (Internet Security Association and Key Management Protocol) Security
Association, which is a secure channel for IKE to negotiate keying material for the IP datagrams. Unlike IPsec SAs, the ISAKMP security associations are bidirectional, so only one is needed.

How IKE negotiates keying material in the Phase 1 exchange is configurable. IKE reads the configuration information from the /etc/inet/ike/config
file. Configuration information includes the interfaces that are affected, the algorithms that are used, the authentication method, and if PFS is used. The two authentication methods are pre-shared keys and public key certificates The public key certificates can be self–signed, or they can be issued
by a Certificate Authority (CA) from a PKI (Public Key Infrastructure) vendor. Vendors include iPlanetTM Certificate Management System, Entrust, and Verisign.